Method and apparatus for automatically sewing belts

Abstract

A method and apparatus are disclosed for forming a loop in a seat belt and stitching the looped belt plies together. One sewing machine performs the strength forming stitch pattern such as the butterfly stitch and it is used as a master sewing machine whose sewing time of operation is maximized. During the stitching of butterfly pattern, another seat belt will have been fed into a loop forming means at which a loop is formed and its looped belt plies will have been tacked together by another sewing machine sewing a zigzag stitch. An automatic transfer means transfers looped belts from the first sewing station to the butterfly stitching machine. An automatic bobbin changing apparatus is also provided.

What is claimed is: 
     
       1. A method of folding an end of safety belts to form a loop and sewing the folded end at a first sewing station and sewing the belt at a nearby second sewing station, such method comprising the steps of: sewing at the second station a previously looped first belt sewn at a first sewing station with a number of lines of stitches in a predetermined second stitch pattern to provide strength to resist tensile forces applied to the belt loop,   during the time of sewing the second stitch pattern folding an end of another belt by a folding device to form a loop therein at a folding station,   during the time of sewing the second stitch pattern and in timed relationship thereto sewing a first stitch pattern to hold the superimposed plies of the belt looped end together, and   shifting the other belt from the first sewing station toward the second station and shifting the first belt from the second station so that the second sewing station is kept occupied by sewing through a preponderance of the time of its operation.   
     
     
       2. A method in accordance with claim 1 in which the sewing of the plies together at the first station comprises the step of sewing a line of stitches in a zigzag pattern across the belt. 
     
     
       3. A method in accordance with claim 1 in which a succession of looped belts stitched by said first station are located between said first sewing and said second sewing station and move in seriatim fashion to the second station. 
     
     
       4. A method in accordance with claim 1 including the step of simultaneously transferring a belt from said first sewing station and transferring another belt into said second sewing station by a common transfer means. 
     
     
       5. A method in accordance with claim 1 including feeding a belt into said first station simultaneously with a discharge feeding of a belt from the second sewing station. 
     
     
       6. A method in accordance with claim 1 including the further step of automatically changing the bobbin of said second sewing machine during the time of belt movement. 
     
     
       7. A method of folding a safety belt end into a loop and to sewing same to resist tensile loads applied to the loop, said method comprising the steps of: feeding a belt to a folding station,   folding an end of the belt to provide face-to-face plies to form a loop at the folding station,   securing the loop plies to each other,   shifting the loop end of the belt to a sewing station,   sewing the face-to-face plies at the sewing station with a predetermined stitching pattern to withstand the tensile loadings to be applied to the loop,   discharge feeding the sewn and looped belt from the sewing station, and   changing a bobbin containing thread for a sewing machine at said second station during the time interval of feeding said belt at said second station, said step of securing the loop plies together comprising sewing them with a sewing machine and with a stitch pattern having substantially fewer stitches than the subsequent stitching operation.   
     
     
       8. A method in accordance with claim 7 including the step of sewing a zigzag stitch pattern to holding the leading end of the belt to a facing belt ply and sewing the plies together with a butterfly stitch pattern. 
     
     
       9. A method of forming and sewing a loop end in a safety belt comprising the steps of: feeding a belt forwardly along a first path to a loop-forming station,   folding over an end of said belt by a folding device at said loop-forming station to form a looped end,   shifting the looped end into a first sewing station,   stitching the folded plies with a first predetermined stitching pattern to hold the loop in the belt at said first sewing station,   transferring the stitched and looped belt along a second path to a nearby second sewing station, sewing a second stitching pattern during the time of stitching of folded plies of another belt at said first station to permanently attach said looped belt plies at said second stitching station against separation under tensile loading of a predetermined value, and   discharging said belt with said loop from said second stitching station.   
     
     
       10. A method in accordance with claim 9 including folding the loop, shifting the loop into said first sewing station, and sewing said first stitch pattern during the time of making the second stitching operation. 
     
     
       11. A method in accordance with claim 9 in which said first stitching pattern is a zigzag pattern and in which said second stitching pattern is a butterfly stitching pattern. 
     
     
       12. A method in accordance with claim 9 including the further step of changing a thread carrying bobbin for a second sewing machine during the time interval for discharging a belt from said second sewing station and moving another belt into position for sewing at said second sewing station. 
     
     
       13. An apparatus for forming and sewing a loop in a safety belt comprising: feeding means for feeding a belt into a loop-forming station,   folding means at said loop-forming station for folding an end of the belt back onto itself to form a loop defined by two plies at one end of the belt,   means for sewing a first stitch to join the looped plies of the belt together at a first sewing station,   transfer means for transferring said looped end of a safety belt to a second sewing station,   a second sewing means at said second sewing station for sewing said loop end with a second stitch to hold said looped end plies together against a predetermined tensile loading, and   discharge means for discharging said sewing looped belt end having first and second stitches joining the plies together.   
     
     
       14. An apparatus in accordance with claim 13 in which a succession of looped belts are disposed between said first and second sewing stations and in which said means for transferring said belt comprises means for transferring through a plurality of positions intermediate said first and second stations before inserting the safety belt into said second sewing station. 
     
     
       15. An apparatus in accordance with claim 14 in which said transfer means comprises a plurality of pushers each engaging one of said belts and joined for conjoint movement to shift a first belt from said first sewing station to an intermediate position and another belt at an intermediate position into said second station. 
     
     
       16. An apparatus in accordance with claim 13 in which said folding means comprises a retractable finger means and a turnover member for turning an end of the belt over the finger means to form said loop. 
     
     
       17. An apparatus in accordance with claim 16 in which a shuttle means carries said folding means and the folded belt to said first sewing machine. 
     
     
       18. An apparatus in accordance with claim 13 in which a flat surface means supports said belts for movement in a first direction by said feeding means and for movement in a lateral direction by said transfer means and then for movement in an opposite direction from said infeed direction for discharge. 
     
     
       19. An apparatus in accordance with claim 13 in which said feeding means comprises a feed wheel for feeding the web forwardly until a length sensor means determines that the belt is in position for folding said folding means. 
     
     
       20. An apparatus in accordance with claim 19 in which said feeding means comprises a continuously rotating feed wheel and in which an actuating means under the control of said length sensing means shifts said feed wheel from said belt to stop feeding of said belt. 
     
     
       21. An apparatus in accordance with claim 20 in which said feeding means and said transfer means each comprise means for pivotally mounting the same for movement into engagement with or from engagement with a belt. 
     
     
       22. An apparatus in accordance with claim 21 including a clamping means for clamping a belt against movement after feeding into said folding means. 
     
     
       23. An apparatus in accordance with claim 18 in which a holddown means engages the upper surfaces of the belts and holds the same against said flat surface to prevent skewing of the same during lateral movements by said transfer means.